Ultra-High Sensitivity Ultrasonic Sensor with an Extrinsic All-Polymer Cavity.

An ultra-high sensitivity ultrasonic sensor with an extrinsic all-polymer cavity is presented. The probe is constructed with a polymer ferrule and a polymer-based reflection diaphragm. A specially designed polymer cover is used to seal the cavity sensor head and apply pretension to the sensing diaphragm. It can be manufactured by a commercial 3D printer with good reproducibility. Due to its all-polymer structure and high coherence depth, the sensitivity of our proposed sensor is improved significantly compared with that of the other sensor structures. Its sensitivity is 189 times as great as that of the commercial standard ultrasonic sensor at the ultrasonic frequency of 50 KHz, and it has a good response to ultrasonic within the frequency range of 18.5 KHz-200 KHz.

A Taper-in-Taper Structured Interferometric Optical Fiber Sensor for Cu2+ ion Detection.

Copper ion is closely associated with the ecosystem and human health, and even a little excessive dose in drinking water may result in a range of health problems. However, it remains challenging to produce a highly sensitive, reliable, cost-effective and electromagnetic-interference interference-immune device to detect Cu2+ ion in drinking water. In this paper, a taper-in-taper fiber sensor was fabricated with high sensitivity by mode-mode interference and deposited polyelectrolyte layers for Cu2+ detection. We propose a new structure which forms a secondary taper in the middle of the single-mode fiber through two-arc discharge. Experimental results show that the newly developed fiber sensor possesses a sensitivity of 2741 nm/RIU in refractive index (RI), exhibits 3.7 times sensitivity enhancement when compared with traditional tapered fiber sensors. To apply this sensor in copper ions detection, the results present that when the concentration of Cu2+ is 0-0.1 mM, the sensitivity could reach 78.03 nm/mM. The taper-in-taper fiber sensor exhibits high sensitivity with good stability and mechanical strength which has great potential to be applied in the detection of low Cu2+ ions in some specific environments such as drinking water.

Analysis of hollow-core photonic bandgap fibers for evanescent wave biosensing.

Hollow-core photonic bandgap fiber (HC-PBGF)-based evanescent wave biosensors are demonstrated and analyzed theoretically and experimentally. With 95% of the guided light power residing in the samples, the measured absorbance for a 30-cm-long fiber filled with a 0.2 microM Alexa Fluor 700-labeled DNA Oligo solution is 1.06. This is in good agreement with the theoretical prediction, which is evaluated by using the refractive index scaling law. The HC-PBGFs thus offer both efficiency and simplicity for the detection of biomolecules in ultra-small sample volumes.

High-resolution photonic bandgap fiber-based biochemical sensor.

The use of photonic bandgap fibers (PBGF) for biomedical sensing has been demonstrated. The demonstrated PBGF has a blue wavelength shift of 280 nm in the falling photonic bandgap edge (PBE) when the ambient refractive indices inside the holey region change from 1.333 to 1.39, which agrees well with the analytical prediction. Combining this with the knowledge of immobilization techniques and biorecognition elements could open up a new class of PBGF-based label-free biosensors. A sensitivity on the order of 0.1 nmol/L could be achieved by consuming less than 1 microL of sample.